normal

adjective

1. conforming with or constituting an accepted standard, model, or pattern; esp., corresponding to the median or average of a large group in type, appearance, achievement, function, development, etc.; natural; usual; standard; regular
2. Biol. occurring naturally normal immunity
3. Chem.
   1. designating or of a salt formed by replacing all the replaceable hydrogen of an acid with a metal or metals
   2. designating or of a solution which contains an amount of the dissolved substance chemically equivalent to one gram atom of hydrogen per liter of solution
   3. designating or of a fatty hydrocarbon, the chain of which is continuous rather than branched, in which no carbon atom is united directly to more than two others
4. Math. perpendicular; at right angles
5. Med., Psychol.
   1. free from disease, disorder, or malformation; specif., average in intelligence or development
   2. mentally sound

Etymology: L normalis < norma, a rule: see norm

noun

1. anything normal
2. the usual state, amount, degree, etc.; esp., the median or average
3. Math. a perpendicular; esp., a perpendicular to a line tangent to a curve, at its point of tangency